Uriel's "plot" was to basically reverse what the lie did to Harry. By sending him out as a ghost to see the huge impact his absence has created in Chicago, and showing him even his ghost can have such a huge impact, Uriel was basically telling him that he doesn't deserve to die. And from what he saw, he realized people like Murphy needed him. He realized his daughter was in a position of such security that his actions won't threaten her. He saw that Thomas was a wreck who blamed himself for Harry's death... Basically, he saw that his "death" did more harm than good.

Along the way, Harry and Bob figure out that Harry wasn't dead. So, later, when Uriel gave him the choice between continuing as a ghost operative and going into an unknown place, Harry knew that represented life. And he chose it, because he saw he had a lot to do. And when he did, Uriel did his final balancing act and told him he needn't be Mab's automaton.

In the end, Ghost Story, while being a great character story, served the bigger purpose of allowing Harry this whole new awesome power (of Winter Knight), while having him mentally ready so it doesn't consume him. This was needed to make the beefing up of his power believable, a kind of explanation for why the Ring won't corrupt Gandalf if he uses it, in this case.